Handling test length bloat

The length of test cases is a little investigated topic in search-based test generation for object-oriented software, where test cases are sequences of method calls. While intuitively longer tests can achieve higher overall code coverage, there is always the threat of bloat – a complex phenomenon in evolutionary computation, where the length abnormally grows over time. In this paper, we show that bloat indeed also occurs in the context of test generation for object-oriented software. We present different techniques to overcome the problem of length bloat, and evaluate all possible combinations of these techniques using different starting lengths for the search. Experiments on a set of difficult search targets, selected from several open source and industrial projects, show that controlling bloat with the appropriate techniques can significantly improve the search performance. Copyright c © 2011 John Wiley & Sons, Ltd.